1. Field of the Invention
The present invention relates to a clamping device of the type adapted to hold and fix a rod by a collet and is a technique favorable for clamping, for example a support rod of a work support for a machine tool at a predetermined height.
2. Description of the Earlier Technology
There is such a clamping device of this collet-type as constructed to diametrically contract the collet by engaging a tapered internal surface of a cylindrical transmission member with a tapered external surface of the collet and to hold and fix a support rod by that diametrically contracted collet (for example, Japanese Utility Model Publication No. 6-7868 proposed previously by the Assignee of the present Application).
By the way, when increasing the foregoing holding and fixing force, it is necessary to decrease a taper angle for engagement.
In the above-mentioned technique, however, when the taper angel for engagement is decreased, since a static friction force acting between the engaged surfaces is increased at the beginning of disengagement, the disengagement becomes impossible due to that large static friction force.
Therefore, in the prior art, the taper angle for engagement could be set merely to a small value from about 6 degrees to about 10 degrees, so that the increasing of the holding and fixing force was limited.